Questions are being raised about the benefits of a $100 million equity investment into a corporate farmer by a Commonwealth agency tasked with lowering carbon emissions.

In February last year the Clean Energy Finance Corporation announced it had secured a $100m equity stake in Viridis Ag - the cropping arm of Macquarie Infrastructure and Real Assets.

The investment was touted as generating "transformational technology" but critics argue much of the money has been spent on already proven farming practices.

Viridis owns five cropping enterprises in Western Australia and two in NSW, which include pastoral land converted to grains production.

CEFC said Viridis was selected for its geographic spread, scale in operations, and access to capital.

In response to questions, the CEFC did not detail what advances in cropping techniques and equipment its investment would help develop, and it declined to share any plans for extension programs, to share benefits derived from Viridis with the farming community.

It sounds like they are copying and pasting work on soil and CTF (controlled traffic farming) by non-profit groups. - Western Australian No Tillage Farming Association executive director David Minkey

However, many farmers have already invested in these practices because of the economic benefits and it is likely that Viridis would have followed suit, even without Viridis' equity funding.

The Western Australian No Tillage Farming Association (WANTFA) is a state-wide, not-for-profit grower group. Executive Director Dr David Minkey questioned the benefits of the CEFC's investment in Viridis.

"Without knowing the devil in the detail of operations on each farm, it sounds like they are copying and pasting work on soil and CTF (controlled traffic farming) by non-profit groups," Dr Minkey said.

"There may be a whole heap of science beyond what's been published, but without detail we don't know.

"But there's nothing I can see in desired outcomes that you'd need to make a proper assessment of the project."

Controlled traffic farming has been used in Australian cropping systems for more than 20 years and has been backed by sustained research and development investment and extension programs from public bodies and grower groups.

Mr Minkey emphasised that it was impossible to make a definitive judgement without more information on the project, but questioned the need for public funding.

"It does sound like Viridis is getting funded to do stuff that farmers are doing anyway, because it makes economic sense for them to do it," he said.

CEFC equity lead Rory Lonergan told this publication last year the investment with Viridis would provide a benchmark of best practice energy consumption, which could be used to help lower carbon emissions across the cropping industry.

The project was inspired by the successful energy benchmarking CEFC has employed in the property sector.

CSIRO and Macquarie Bank will collaborate with the CEFC on the Viridis project to develop a methodology that farmers can use to rate their energy consumption against production output.

That could mean becnhmarking carbon emission reductions from low-energy production systems, improvements to soil and water resources - and potentially soil carbon capture.

Such data could potentially provide a benchmark for an environmental stewardship fund, to pay farmers for public benefits generated on their land.

Despite the potential upside, there are questions around why CEFC would need to provide equity funding to a corporate farmer to enable CSIRO to benchmark its data.

Using this data could generate a financial benefit for a corporate farmer by enabling it to participate in direct action emissions reduction schemes.

CEFC's investment into the established controlled traffic and soil amelioration systems dwarfs the extension budget of even the largest levy-payer funded organisations.

The industry's largest such organisation, the Grains Research and Development Corporation, has a total budget of $200m and wouldn't spend a fraction of CEFC's stake in Viridis on cropping extension programs. Smaller cropping groups would struggle to fund $1m a year for extension.

Since it was founded in 2012, The CEFC has issued more than $200 million of loans to more than 790 Australian agricultural projects.

The CEFC supports investment up to $5 million into energy efficient equipment and facilities, low-emission energy generation, solar power and methane capture.

Funds are made available in partnership with banks with a 0.7 per cent discount.